Functional genomics requires reliable methods to investigate the consequences of disrupting the gene function. Since its discovery in C .elegans, RNA interference (RNAi) has become an invaluable resource to tackle gene function in cell culture, mammals and invertebrate model systems. However, but it has proven a major challenge to apply this technique in zebrafish and Xenopus. In this proposal we will apply our current knowledge in the microRNA (miRNA) field to develop several strategies that improve RNAi. This proposal will provide specific rules to the scientific community to improve RNAi in zebrafish to allow the functional characterization of the zebrafish genes. In the future, the resuls derived from this project will establish a frame work to understand the structure and the function of vertebrate genes.